1. Field of the Invention
The present invention relates to a thermal analysis apparatus in which a heating furnace is cooled by a supply of a cooling gas.
2. Description of the Related Arts
Hitherto, in the thermal analysis apparatus such as differential scanning calorimeter, an analysis is performed by possessing the heating furnace, accommodating in its inside a sample (specimen), and measuring an egress-and-ingress of a heat of the sample with its heat quantity by changing a temperature of the sample by raising or lowering it using heating and cooling apparatuses. In the thermal analysis apparatus like this, there is one in which the heating furnace is temperature-controlled, e.g., by cooling the heating furnace by supplying a gas, which is cooled by a liquefied refrigerant, to the heating furnace, and heating the heating furnace by a heater provided in the heating furnace, or the like. In a case performing the cooling, there is one in which a control for flowing the cooling gas is performed by opening/closing, in compliance with a necessity, an electromagnetic valve provided between a liquefied refrigerant supply device and the heating furnace (e.g., refer to Japanese Patent No. 3066687 Gazette and JP-B-7-122619 Gazette).
Japanese Patent No. 3066687 is one in which the cooling of the heating furnace after a measurement finish in the thermal analysis apparatus is automated to thereby contrive a labor saving in a measurement and an improvement in an efficiency, and is one in which there is made such that, if a measurement finishes, the cooling of the heating furnace is automatically started by making the electromagnetic valve ON to thereby flow the cooling gas of a constant quantity, the cooling is automatically stopped if the heating furnace is cooled to a cooling stop temperature previously set and, in a case where a temperature of the heating furnace rises again by a thermal inertia or the like, it is cooled to or below a set temperature in a short time by automatically performing a re-cooling.
JP-B-7-122619 Gazette is one in which there is disclosed about a constitution of a full automatic gas cooling by liquefied nitrogen, one in which there is made such that there is previously set a temperature program in which a temperature change in regard to an elapse of time is programmed, there are performed, so as to follow that temperature program, a cooling control of a sample chamber (heating furnace) by a supply electric power regulator together with the elapse of time, and a temperature control of the sample chamber by a heating of the heater, and one in which a temperature of the sample chamber is precisely controlled from a temperature lower than a chamber temperature, which reaches to a liquefied refrigerant temperature, to a high temperature of about 700° C.
However, in the thermal analysis apparatus used in the Patent Documents 1 and 2, there are issues like the below.
In Japanese Patent No. 3066687 Gazette and JP-B-7-122619 Gazette, if cooled by flowing the cooling gas to the heating furnace becoming such a high temperature as to exceed 700° C. for instance, there is an issue that the heating furnace comprising ceramic is cracked and damaged by a thermal influence exerted on the heating furnace. Therefore, generally, it is lowered by a natural cooling to about 700° C. deemed to be a temperature, at which the heating furnace is not cracked, from such a high temperature as to exceed the above 700° C. and, after the heating furnace becomes 700° C. or below, the cooling gas is supplied to the heating furnace. However, depending on the measurement, there is such a demand that it is desired to measure by lowering the temperature faster than the natural cooling in a higher temperature region than the above 700° C., so that a suitable cooling method is requested.
Further, in a case controlled only by ON/OFF of the electromagnetic valve like Japanese Patent No. 3066687 Gazette and JP-B-7-122619 Gazette, as mentioned above if cooled by opening the electromagnetic valve at a time point becoming 700° C. or below, it follows that the temperature of the heating furnace rapidly lowers, and there is a defect that a quick change in the temperature makes a feedback control of the heater difficult, so that there is a drawback that a precise temperature control of the heating furnace is impossible. Therefore, there is an issue that an accurate measurement result is not obtained.
The present invention is one made in view of the issues mentioned above, and its object is to provide a thermal analysis apparatus made so as to cool the temperature of the heating furnace without damaging the heating furnace by supplying the cooling gas of a suitable flow rate.